Manufacturers in the electronics industry use automatic test systems or testers to test various electronic components, integrated circuits (ICs) and other devices under test (DUTs) to cull out defective devices. For example, data patterns are delivered to an integrated circuit with specific timing and voltage settings through timing generators and pin electronic channels to test the functionality of the integrated circuit. Data is then read from the integrated circuit to ensure that the device responds correctly. A variety of parametric timing tests may also be performed to validate correct operation of the integrated circuit as well as adherence to its specifications. Generally, it is desirable to test integrated circuits at several points during the manufacturing process, including while they are still part of a wafer or substrate.
Equipment used in wafer testing can include a wafer prober and an automated test system. A conventional wafer prober has a movable chuck which serves to transport the wafer to a position underlying a probe card mounted to the top deck of the wafer prober by being clamped at its periphery. A probe array is typically provided on the underside of the probe card for engaging the bonding pads of one or more die on the wafer. A plurality of contact elements, electrically coupled with the probe array, are usually provided at the periphery on the top of the probe card. The automated test system includes one or more testers which overlie the top deck of the wafer probe and have an electrical interface for electrically engaging the contact elements of the probe card.
Unfortunately, changes in temperature and mechanical forces experienced by the probe card during testing can result in distortion of the probe card, thus deflecting the generally unsupported central portion of the probe card where the probe array is located. The larger the probe card, the more deflection can occur in the probe card. Such distortion of the probe card can result in undesirable alignment errors between the probe array of the probe card and the chuck, thus compromising the accuracy or completeness of the testing of die carried by the chuck.
In view of the foregoing, it would be desirable to minimize distortion of the probe card, particularly in the vicinity of the probe array mounted to the underside of the probe card.